Women with hypertensive pregnancies are 4× more likely to develop chronic hypertension. Previously, we showed a short period of blood pressure (BP) self-management following hypertensive pregnancy resulted in persistently lower BP after 6 months. We now report the impact on long-term BP control. Women who participated in the postpartum randomized controlled trial, SNAP-HT (Self-Management of Postnatal Hypertension; NCT02333240), were invited for 24-hour ambulatory and clinic BP measures. Height and weight were measured by calibrated scales and standardized tape measures, activity by 7-day wrist-worn accelerometer, and dietary factors assessed by questionnaire. Sixty-one of 70 eligible women were followed up 3.6±0.4 years after their original pregnancy. Twenty-four-hour diastolic BP was 7.0 mm Hg lower in those originally randomized to postpartum BP self-management instead of usual care. This difference remained significant after adjustment for either BP at the time of delivery (-7.4 mm Hg [95% CI, -10.7 to -4.2]; P<0.001) or pregnancy booking BP (-6.9 mm Hg [95% CI, -10.3 to -3.6]; P<0.001). Adjustment for current salt intake, age, body mass index, waist-to-hip ratio, arm circumference, parity, alcohol intake, and physical activity had no effect on this difference. Reductions in diastolic BP at 6 months, following self-management of BP postpartum, are maintained 3.6 years later as measured by lower 24-hour diastolic BP. Interventions to optimize BP control during the puerperium in women with hypertensive pregnancies improve BP in the longer term, in a cohort at increased risk of developing chronic hypertension and major adverse cardiovascular events. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT02333240.